An image reader is used as a device for optically reading an image on a medium. The image readers can largely be classified into three types of a flat bed type, a sheet feed type, and a handy type. The flat bed and the sheet feed type of image readers are stand-alone devices on which a document is set and read. On the other hand, the handy type of image reader has a smaller size as compared to the other two types described above, so that this type of image reader can easily be connected to a laptop computer or a PDA (Personal Digital Assistant). In the handy type of image reader, because a document is manually scanned, it is necessary to specify a position for start of reading (read start position) and give instructions for start and end of reading to the device. Conventionally it is necessary to set the image reader at the read start position and press operation switch provided on a housing thereof.
FIG. 110 is a perspective view showing appearance of an image reader 1 based on the conventional technology as described above. The image reader shown in this figure comprises a slender box-shaped housing 2, an operation switch 3 provided on a top surface of the housing 2, and a cable 4. In this image reader 1, when an image on a document P placed under an image reading surface 2a is to be read, the housing 2 is set at the read start position and the operation switch 3 is pressed to indicate a read start position. While pressing down the operation switch start of reading (read start) is instructed by manually moving the image reader in the direction V (the scanning direction) indicated by an arrow, and the image is read. When the image reader is moved to an end of reading position (read end position) and the operation switch 3 is pressed again the reading is stopped.
FIG. 111 is a perspective view showing appearance of another image reader 10 based on the conventional technology. The image reader 10 comprises a housing 11 having an image reading surface 11a, an interface card 12 connected to an insertion port 15a of a main system of the device 15, and an image reading section 13 for reading an image. In the image reader 10 having the configuration as described above, by connecting the image reader 10 via the interface card 12 to the main system 15, image data read by the image reading section 13 can be sent to the main system. Also in the conventional technology, in addition to the configuration as described above in which the image reader 10 is connected to the main system 15 via the interface card 12 as shown in FIG. 111, there is known an image reader as shown in FIG. 112 having a configuration in which a connector 21 attached to an end of a cable 22 is connected to the interface card 12.
In the image reader based on the conventional technology as described above, image is read based on the flow chart shown in FIG. 113. In step TA1 shown in this figure, a user gives an instruction for read start by contacting the image reader to a document and then pressing an operation key (for instance, the operation switch 3 shown in FIG. 110). In step TA2, image data for several lines is read from one line on the document, and a threshold value for digitizing (conditions for reading) used for digitizing image data is decided based on the color of characters and the color of the background.
In step TA3, an operation for reading an image on the document is started, image data read as described above is compared with the threshold value, and monochrome image data is generated. The threshold value for digitizing is decided each time the document is read. The operation sequence as described above is employed because it is necessary to generate sharp monochrome image data by deciding a threshold value corresponding to a quality of the paper used.
Further in the image readers based on the conventional technology as described above, in order to downsize the device and reduce power consumption various types of measures are taken such as use of a compact and low power consumption microprocessor having a high processing speed or the like. In such image readers, after the image data is read, a sequence of operations for post-processing comprising correction of an inclination of an image, contraction of corrected image data, recording and storage of the contracted image data is executed. When the sequence of operations for post-processing is finished, the next image read processing is performed.
FIG. 114 is a block diagram showing configuration of the image reader based on the conventional technology. A read instructing section 30 issues an instruction for reading an image on a document to a read control section 31. The read control section 31 gives an instruction for reading an image on the document to an image reading section 32 upon input of the instruction for read start from the read instructing section 30 as a trigger, and also gives an instruction for starting an operation for writing (storing) image data as a result of reading by the image reading section 32 to a buffer memory 33. Further, the read control section 31 gives an instruction for starting an operation of reading image data from the buffer memory 33 to a data processing section 34 when image data write in the buffer memory 33 is finished. The data processing section 34 reads out image data from the buffer memory 33 upon an instruction from the read control section 31 described above, and executes the sequence of operations for post-processing as described above to the image data. The image data having been subjected to the post-processing by the data processing section 34 is stored in the data storing section 35.
Operations of the image reader is explained with reference to FIG. 115 and FIG. 116. In step TB1 shown in FIG. 115, the read control section 31 determines whether an instruction for read start has been issued from the read instructing section 30 or not, and when it is determined that the instruction has not been issued (“No”), the read control section 31 repeats the same operation for determination. When an instruction for read start is issued at the point of time t1 shown in FIG. 116, the read control section 31 determines in step TB1 that start of reading has been instructed (“Yes”), and shifts the processing to step TB2.
In step TB2, the read control section 31 outputs a reading start signal shown in FIG. 116 to the image reading section 32 as well as to the buffer memory 33. With this operation, an image on a document is read by the image reading section 32, and the data obtained as a result of reading is written as shown in FIG. 116 in the buffer memory 33. When the operation for writing the image data for a specified number of lines is finished at a time point ta, the read control section 31 reports completion of the operation for writing image data to the data processing section 34. With this operation, the data processing section 34 reads out the image data stored in the buffer memory 33 as shown in FIG. 116 in step TB3.
The data processing section 34 executes the sequence of operations for post-processing described above with respect to the data. Then the data processing section 34 reports to the read control section 31 that the sequence of operations for post-processing has been executed. Then in step TB1, the read control section 31 determines whether an instruction for read start has been issued from the read instructing section 30 or not. As described above, in the image reader based on the conventional technology it is clearly understood from FIG. 116 that, after image data is written in the buffer memory 33 the image data is read out from the buffer memory 33. Namely, in the image reader based on the conventional technology, write processing and read processing are executed serially.
In the image readers based on the conventional technology as described above, however, as shown in FIG. 110, after the image reader 1 is set at a read start position on a document P, read start is started once by pressing the operation switch 3, image is read by scanning the document P with the help of the image reader, and the operation switch is pressed again when terminating the operation for reading an image, and thus the troublesome switch operations are required.
Further, in the image reader based on the conventional technology as described above, the operation switch is repeatedly pressed many times during an operation for reading an image according to specifications of the device, which requires a user to carry out very troublesome operations. Thus, in the image readers based on the conventional technology as described above, a user is required to operate the operation switch many times when reading an image, so that operability and adaptability to practical operations are rather low. Further, differences in user interfaces and troublesome switch operations are very disadvantage us to the user.
Further, in the examples shown in FIG. 111 and FIG. 112, a place for connection of the image reader 10 may be restricted based on a place (insertion port) in the main system 15 for loading the interface 12, and the cable 22 disturbs smooth operation when the image reader 20 and the main system 15 are connected to each other, so that operability and adaptability to practical use is very poor. Further, in the image readers based on the conventional technology as shown in FIG. 111, the specific main system 15 is required, so that downsizing of the device is very difficult.
Further, in the image readers based on the conventional technology, there is the problem that, when fluctuation in read values generated due to non-uniformity of sensitivity of sensors or difference of light sources is very larger, a read image gets disadvantageously degraded. In addition, in the image readers based on the conventional technology as described above, a user can read (scan) an image in any direction and a degree of freedom in the operation is high, but sometimes the image may be a rotated one or a mirrored one in some scanning directions, which is very inconvenient.
In the image readers based on the conventional technology as described above, as described with reference to FIG. 113, it is a requirement for obtaining clear monochrome image data that an instruction for starting an operation for reading an image is given in the state where the image reader is placed on a document. In the image readers based on the conventional technology, however, if an instruction for starting an operation for reading an image is given in a state where the image reader is not placed on a document, in other words in a state where the image reader is held by hands, the space (a place where there is only air and no document or the like) is read. In such a cases, read image data is completely different from the image on a document as an object to be read, so that the threshold value decided according to the image data is not a correct value. When the image data is digitized by using such a threshold value, it is inevitable that the quality of read image gets disadvantageously degraded.
Further, in the image reader described with reference to FIG. 114, write processing and read processing are executed serially as shown in FIG. 116. A time interval from a point of time when an operation for reading an image is finished (time ta) until a point of time when the image reader is ready for a next operation for reading an image (time t2) extends from several seconds up to several tens seconds. Because of this feature, when several images are to be read, a user must wait for several to several tens seconds after an operation for reading of one image is executed until the image reader is ready for an operation for reading of the next image. Namely in the image readers based on the conventional technology, a plurality of images can not be read continuously, so that adaptability to practical use is very low.